Removal of Zinc from Aqueous Solutions Using Lamellar Double Hydroxide Materials Impregnated with Cyanex 272: Characterization and Sorption Studies.

Removal of heavy metals from wastewater is mandatory in order to avoid water pollution of natural reservoirs. In the present study, layered double hydroxide (LDH) materials were evaluated for removal of zinc from aqueous solutions. Materials thus prepared were impregnated with cyanex 272 using the dry method. These materials were characterized through X-ray diffraction (XRD), Fourier transform infrared (FTIR), and thermal analysis. Batch shaking adsorption experiments were performed in order to examine contact time and extraction capacity in the removal process. Results showed that the equilibrium time of Zn (II) extraction is about 4 h for Mg2Al-CO3 and Mg2Al-CO3-cyanex 272, 6 h for Zn2Al-CO3, and 24 h for Zn2Al-CO3-cyanex 272. The experimental equilibrium data were tested for Langmuir, and Freundlich isotherm models. Correlation coefficients indicate that experimental results are in a good agreement with Langmuir's model for zinc ions. Pseudo-first, second-order, Elovich, and intraparticular kinetic models were used to describe kinetic data. It was determined that removal of Zn2+ was well-fitted by a second-order reaction kinetic. A maximum capacity of 280 mg/g was obtained by Zn2Al-CO3-cyanex 272.

Lanthanide recovery by silica-Cyanex 272 material immobilized in alginate matrix.

Mesoporous silica impregnate with Cyanex 272 (bis/2,4,4-trimethylpentyl/phosphinic acid) extractant was immobilized into an alginate matrix to obtain a composite sorbent easy to use and applicable in fixed-bed column continuous systems. The sorption efficiency of this material was tested for the recovery of Eu(III) ions from aqueous solutions in batch and continuous mode. The competition among rare earths ions (europium, lanthanum, and lutetium) and among rare earths and calcium or sodium ions was investigated. High calcium concentrations strongly reduce the sorption capacity of the alginate matrix that composes the hybrid material and the Cyanex 272 impregnated into silica powder improves the rare earths' sorption performance in this calcium charged media. The experimental breakthrough curves obtained were satisfactory fitted by Thomas model.

Boron Removal from Aqueous Solutions by Using a Novel Alginate-Based Sorbent: Comparison with Al2O3 Particles.

Boron removal was evaluated in the present work by using calcium alginate beads (CA) and a novel composite based on alginate-alumina (CAAl) as sorbents in a batch system. The effects of different parameters such as pH, temperature, contact time, and composition of alginate (at different concentrations of guluronic and mannuronic acids) on boron sorption were investigated. The results confirm that calcium alginate beads (CA) exhibited a better adsorption capacity in a slightly basic medium, and the composite alginate-alumina (CAAl) exhibited improved boron removal at neutral pH. Sorption isotherm studies were performed and the Langmuir isotherm model was found to fit the experimental data. The maximum sorption capacities were 4.5 mmol g-1 and 5.2 mmol g-1, using CA and CAAl, respectively. Thermodynamic parameters such as change in free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were also determined. The pseudo-first-order and pseudo-second-order rate equations (PFORE and PSORE, respectively) were tested to fit the kinetic data; the experimental results can be better described with PSORE. The regeneration of the loaded sorbents was demonstrated by using dilute HCl solution (distilled water at pH 3) as eluent for metal recovery.